This specification relates to Internet search engines.
Internet search engines aim to identify resources, e.g., web pages, images, text documents, multimedia content, e.g., videos, that are relevant to a user's information needs and to present information about the resources in a manner that is most useful to the user. Internet search engines generally return a set of search results, each identifying a respective resource or otherwise providing a particular type of information, in response to a user submitted query.
In general, a search system receives a search query and obtains search results that satisfy the search query. The search results identify resources that are relevant or responsive to the search query, e.g., Internet accessible resources. A search system can identify many different types of search results in response to a received search query, e.g., search results that identify web pages, images, videos, books, or news articles, search results that present driving directions, in addition to many other types of search results.
Search systems may make use of various subsystems to obtain resources relevant to a query. For example, a search system can maintain a knowledge base that stores information about various entities and provide information about the entities when a search query references the alias of an entity. The system can assign one or more text string aliases to each entity. For example, the Statue of Liberty can be associated with aliases “the Statue of Liberty” and “Lady Liberty.” Aliases need not be unique among entities. For example, “jaguar” can be an alias both for an animal and for a car manufacturer.
Another example search subsystem is a part-of-speech tagger. The part-of-speech tagger analyzes terms in a query and classifies each term as a particular part of speech, e.g., a noun, verb, or direct object. Another example search subsystem is a root word identifier. Given a particular query, the root wood identifier can classify a term in the query as a root word, which is a word that does not depend on any other words in the query. For example, in the query “how to cook lasagna,” a root word identifier can determine that “cook” is the root word of the query.